This invention relates to a foam molding method and a mold assembly to be preferably used in molding seat pads for seats of vehicles. More particularly it relates to a foam molding method and a mold assembly which enhance aesthetic appearance of rear side pad of a seat back and enable front and rear side pads to be molded from two foaming materials different in characteristics (physical properties provided in JASO-B408 and properties depending upon variance in combination of hot and cold cure foams).
The term "seat pads" used herein is intended to include cushion pads of seats and pads of seat backs.
In a conventional method of producing seat pads for automobiles, for example, a foamed body is molded from a single foaming material and thereafter a foamed body different in characteristics from the first molded foamed body is attached to a principal part of the first molded foamed body.
In another method, as shown in FIG. 1 into a first foaming stock solution 2 proceeding with its foaming in a lower mold 1 a second foaming stock solution is forced. Then, the lower mold 1 and an upper mold are closed in a horizontal plane as shown in phantom lines in the drawing and heated and cooled in succession. Alternatively, as shown in FIG. 2, a foaming stock solution 5 is poured onto a foamed body 4 previously arranged in a lower mold 1, and an upper mold and the lower mold are closed, heated and cooled. These methods somehow obtain automobile seat pads made of two kinds of foaming materials different in characteristics.
Among these methods, with the method including the step of attaching a foamed body to a previously foamed body, a process for the attaching step is needed to increase a cost of the seat pad. Moreover, there is a risk of unaesthetical appearance due to positional a shift of the attached foamed body relative to the previously foamed body.
In the method of the prior art shown in FIG. 1, the foaming stock solutions of two different kinds cannot be effectively prevented from mixing with each other so that it is very difficult, if not impossible, to realize expected cushion characteristics of the produced seat pad which is poor in reproducibility of quality of the products.
In the method of the prior art shown in FIG. 2, moreover, increase in process and cost caused by the step of setting the foamed body 4 in the lower mold 1 cannot be avoided and impregnated layer of the foamed body 4 with the foaming stock solution 5 detrimentally affect cushion characteristics of the seat pad.
Other than the above described methods of the prior art, there is a method disclosed by the assignee of this application in Japanese Patent Application Laid-open No. 60-240,414.
In this method, there are provided a fixed mold, a movable mold rotatable relative to the fixed mold and forming a cavity in cooperation with the fixed mold and a core member forming an inwardly facing flange of a foamed product about a back surface forming member positioned in a center of the movable mold. At least part of the core member is rotatable in upper and lower directions. In foam molding by the use of the mold assembly, after a foaming stock solution is poured into the fixed mold, the movable mold is rotated relative to the fixed mold to close the fixed and movable molds which are then maintained in a substantially horizontal position, thereby causing the foaming stock solution to flow onto a back side of the core member during foaming of the solution to produce a foamed product having the inwardly facing flange on the back surface.
In such a prior art, process however, foam molding is effected by causing the foaming stock solution poured in the fixed mold to flow onto the back surface side of the core member during foaming of the solution. Therefore, on the inwardly facing flange formed by the function of the core member or on the back surface of the foamed product, marks of flowing of the foaming stock solution would arise due to long flow distances during foaming to detrimentally affect the appearance of the foamed product. In addition, it is substantially impossible to mold front and rear portions of a foamed product from two kinds of foaming materials different in characteristics.